The goals of the proposed research are to (1) determine the extent to which cocaine-takinghistory affects the reinforcing strength of cocaine, (2) to determine the extent to which cocaine-taking historyaffects the reinforcing strength of food, and (3) to determine the degree to which a long cocaine history causes compulsive cocaine use. The first of the proposed experiments will examine the effects of cocaine history on the reinforcing strength of cocaine. This will be accomplished by assigning two groups of animals to a short or long history (determined by the number of sessions) of cocaine self-administration. Following the respective history of each group, the elasticity of demandfor cocaine will be measured using a demand curve where the number of earned cocaine reinforcers will be plotted as a function of cocaine's price (the number of responses required for a single cocaine reinforcer). Demand analysis is used because it is to date, the most valid assay for quantifying the reinforcing strength of a given reinforcer. The second experiment will examine the effects of a long cocaine self-administration history on the elasticity of food demand using a procedure similar to that described for Exp. 1 except that following the drug history, the elasticity of food will be assayed. A third experiment will be performed to determine the degree to which a long cocaine history causes compulsive use of cocainethat leads to the loss of a natural reinforcer (food). This will be accomplished by comparing the number of cocaine and food reinforcers chosenwithin a discrete trials, mutually-exclusive choice procedure. The results from these experiments could provide profound insight into the processes underlying drug addiction, namely, the capacity for addictive drugs such as cocaine to increase in their reinforcing strength with increased drug use and the capacity for natural rewards such as food to decrease in their rewarding strength with increased drug use. In addition, the proposedwork could provide a model showing the capacity of addictive drugs to increase compulsive drug with increased drug experience at the expense of serious negative consequences, such as the loss of food. Altogether, such findings will be important for the further study of behavioral and neurobiological variables involved in producing drug addiction and for the development of treatments for this disease.